1. IB Biology Topic 2 Internal Assessment
Osmosis in Potatoes
IB Biology
Topic 2
Internal Assessment

2. Now your turn!! Lesson 1: -pre-lab
-carrying out a standardised practical using handouts I will give you
-familiarising yourself with working in a lab and thinking about how you could adapt the experiment for an Internal Assessment
Lesson 2:
-Using your Design Lab Training Sheet you will work in teams to design a practical investigating an aspect of osmosis.
Lesson 3:
-You will carry out the practical and collect data as a team.
Lesson 4 + 5:
-I will show you how to process your data with statistics!
-specifically using Excel to calculate means, standard deviations and draw graphs
Lesson 6:
-I will guide you on how to write a conclusion and evaluation
Lesson 7:
-Your practical will be handed in
-written up individually and in the correct format
-self assessment should be complete as well

3. Pre-lab
3 cm
3 cm

4. Writing A Statement of the Problem for the Experiment
What should it state?
It should state: “The Effect of the Independent Variable on the Dependent Variable”.
A good statement of the problem for “Rate of photosynthesis” would be
The effect of light intensity on the rate of photosynthesis

5. More about our variables:
The independent variable is the variable that is purposely changed. It is the manipulated variable.
The dependent variable changes in response to the independent variable. It is the responding variable.
What is the “photosynthesis” independent variable?
Light intensity measured in Lux
What is the dependent variable?
Volume of O2 produced per minute

6. Title for the photosynthesis experiment
The effect of light intensity on the rate of photosynthesis of Elodea

7. Another Look at Our Hypothesis
INDEPENDENT VARIABLE
If the light intensity increases,
DEPENDENT VARIABLE
then the rate of photosynthesis will increase.
To make this IB worthy you MUST:
a)Include a sketch graph of your predicted results
b) Give SCIENTIFIC reasoning as to why you predict this

8. Controls in an Experiment
Factors that are kept the same and not allowed to change
What should be kept constant in the experiment?
CONSTANTS
Type of plant
C02 concentration
Time the experiment runs for
Time intervals at which the DV is measured
Wattage of light bulb
Colour of bulb
Temperature of experiment
Time of day

9. Values of the Independent Variable
How many different values of the independent variable should we test?
Enough to clearly illustrate a trend in the data –always use the 5x5 rule for continuous data
e.g. 10cm, 20cm, 30cm, 40cm, 50cm

10. Repeated Trials How many repeated trials are needed in the experiment
At least 5, then calculate n mean value for each level of the independent variable
(this will also give enough data to calculate standard deviation)

11. Drawing of Experiment

12. Now complete your Design Lab sheet as a team!

13. Carrying out your practical…
Qualitative Observations
(must have these or zero for DCP1!!)
It seemed as it the rate of oxygen production started slowly at first but then speeded up
The bubbles of oxygen were all different sizes

14. Quantitative: Sample Data Table
Title: The effect of changing light intensity on the rate of photosynthesis in Elodea
Vol of 02 produced in 5 min (±0.01ml)
TRIALS
Distance of light source
(±1cm)
Mean Vol of 02 produced in 5 min (±0.01ml) 10 20 30 40 50

15. Data Processing for Internal Assessment AND Topic 1

16. Data Processing You need to:
Calculate percentage change for EACH trial of EACH molarity of solution –(why % change and not just change in mass?)
Calculate the mean percentage change for EACH molarity of solution –(why % change and not just change in mass?)
Calculate the error for EACH mean
Plot a graph comparing percentage changes

24. Two classes took a recent quiz
Two classes took a recent quiz. There were 10 students in each class Each class had an average score of 81.5

25. Since the averages are the same, can we assume that the students in both classes all did pretty much the same on the exam?

26. The answer is… No. The average (mean) does not tell us anything about the distribution or variation in the grades.

27. Here are scatter diagrams of the grades in each class:

28. Mean

29. So, we need to come up with some way of measuring not just the average, but also the spread of the distribution of our data.

30. Why not just give an average and the range of data (the highest and lowest values) to describe the distribution of the data?

31. But what if the data looked like this:
Well, for example, lets say from a set of data, the average is and the range is 23.
But what if the data looked like this:

32. Here is the average
But really, most of the numbers are in this area, and are not evenly distributed throughout the range.
And here is the range

33. The Standard Deviation is a number that measures how far away each number in a set of data is from their mean.

34. If the Standard Deviation is large, it means the numbers are spread out from their mean. If the Standard Deviation is small, it means the numbers are close to their mean.
large,
small,

35. Here are the scores on the biology quiz for Team A:72 76 80 81 83 84 85 89
Average:
81.5

36. The Standard Deviation measures how far away each number in a set of data is from their mean.
For example, start with the lowest score, 72. How far away is 72 from the mean of 81.5?
= - 9.5
- 9.5

37. Or, start with the lowest score, 89
Or, start with the lowest score, 89. How far away is 89 from the mean of 81.5?
= 7.5
- 9.5
7.5

38. Now, lets compare the two classes again
Team A
Team B
Average on the Quiz
Standard Deviation

39. Now...how do you do it the easy way?

47. Concluding and Evaluating

48. Conclusion
This is the section where you draw conclusions about the experiment as it relates to your aim and hypothesis. Calculated results should be compared to values from the literature (i.e. accepted values from professional laboratories) where possible. This section should include: • Conclusion based on your Aim or Hypothesis. (using appropriate language) • States the quantitative or qualitative relationship • Correctly interprets the graph of the data • Includes relevant calculated values to support conclusion • Includes some elaboration based on the science being learned

49. Discussion of errors and limitations to the experiment
• Must comment on the “quality” of the results, do they make sense?
• Identifies anomalous results where appropriate (use your SDs to help you do this!)
• Prioritizes errors and suggests where they came from.
• Utilizes the ideas of “systematic” and “random” errors in the discussion
• Indicate what effect the error(s) would have on the results
• Human errors should not be the main source of errors!
• Suggestions for improvements
• Identifies weaknesses in the experiment and suggests realistic suggestions for improvement
• Improvements should help to improve the errors previously identified

50. How to write an effective conclusion
Also known as putting it all together

51. What is a conclusion? A conclusion is a summary of the experiment.
It is putting the hypothesis together with the data and coming up with a conclusion or ending thought.
It is a written answer to the original question.

52. So where to start… Every conclusion begins with a topic sentence.
In a conclusion, the topic sentence is the restatement of the problem/question.

53. Can your group state a hypothesis for the research question below?
The effect of different temperatures on the activity of an enzyme?

54. Can you write a conclusion for the data below?

55. Keep your group’s conclusion close to hand
We will now go through step by step of the format and information that should have been included….

56. Our conclusion outline
1. Restate the Problem This experiment was investigating the affect of different temperatures on enzyme activity.

57. Our conclusion outline
1. Restate the problem
2. Restate your hypothesis
(It was predicted that…)
It was predicted that as the temperature increased from 0°C, the rate of enzyme reaction will increased up until the optimum temperature for this enzyme.
This is the temperature at which the enzyme will be working with maximum efficiency. After this point the rate of reaction will begin to decrease as the enzyme denatures.

58. So was your hypothesis right, wrong or indifferent?
3. Accept or reject your hypothesis Does the data support the hypothesis? If it does-we accept the hypothesis If it doesn’t-we reject the hypothesis My processed data supports my hypothesis

59. Now provide evidence
Provide actual data in sentence form that backs up your previous statement.
What type of relationship was there, if any?
How did the independent variable effect the dependent variable?
Were there any trends?
changes; (increases, decreases in data)
patterns (repeated data that is similar)

60. Our conclusion outline
As the temperature increased from 0°C to 25°C, the rate of reaction also increased until at 25°C where the rate of reaction reached it’s maximum of 1.5 units.
After this temperature the rate of reaction dropped to 0.5 units at 45°C. As the temperature was increased to 65°C the rate of reaction fell to 0 units and stayed at 0 units at 85°C as well.

61. Next Justify your data with scientific theory
As the temperature increases the molecules have greater kinetic energy. This increases the number of collisions thereby increasing the rate of reaction.
As the temperature continues increasing the rate of reaction decreases after the optimum temperature.
This is because the enzyme, which is a protein molecule denatures. The specific 3D structure of the active site is irreversibly changed so it can no longer form an enzyme-substrate complex.

62. Our conclusion outline
1. Restate the problem
2. Restate your hypothesis
(It was predicted that…)
Accept or reject your hypothesis
Provide actual data in sentence form that backs up your previous statement.
Justify your data with scientific theory

63. Yeah! We’re almost there….

64. 6. Concluding sentence This sentence should
Begin with a transition word
To sum up
In conclusion
Therefore, it can be said that
Rephrase the original question or problem
Explain the importance of carrying out the experiment

65. Our conclusion outline
In conclusion, it can be stated that different temperatures do have an affect on enzyme activity.
Therefore, it is possible to deduce the optimum conditions for an enzyme to ensure maximum efficiency of this particular enzyme.

66. 6 points to scientific success!
1. Restate the problem
2. Restate your hypothesis
Accept or reject your hypothesis
Provide actual data in sentence form that backs up your previous statement.
Justify your data with scientific theory
Concluding sentence that justifies the experiment

67. Conclusion
This experiment was investigating the affect of different temperatures on enzyme activity.
It was predicted that as the temperature increased from 0°C, the rate of enzyme reaction will increased up until the optimum temperature for this enzyme.
This is the temperature at which the enzyme will be working with maximum efficiency. After this point the rate of reaction will begin to decrease as the enzyme denatures.
My processed data supports my hypothesis. As the temperature increased from 0°C to 25°C, the rate of reaction also increased until at 25°C where the rate of reaction reached it’s maximum of 1.5 units.
After this temperature the rate of reaction dropped to 0.5 units at 45°C. As the temperature was increased to 65°C the rate of reaction fell to 0 units and stayed at 0 units at 85°C as well.
As the temperature increases the molecules have greater kinetic energy. This increases the number of collisions thereby increasing the rate of reaction. As the temperature continues increasing the rate of reaction decreases after the optimum temperature. This is because the enzyme, which is a protein molecule denatures. The specific 3D structure of the active site is irreversibly changed so it can no longer form an enzyme-substrate complex.
In conclusion, it can be stated that different temperatures do have an affect on enzyme activity. Therefore, it is possible to deduce the optimum conditions for an enzyme to ensure maximum efficiency of this particular enzyme.

68. Evaluation
To evaluate your science experiments simply answer the following questions:
• How could you have improved the way you did your practical?
• What improvements would you make to your method if you did it again? Why?
• Did the data you collected give you enough information? Why?
• What could you do to improve the reliability of your data?

69. Evaluations : What to include... Examples...
Write down how well you think the experiment went and why.
"The experiment went quite well but my human error contributed to unreliable results. This is because….".

70. 3) Point out any odd results that you had
"Looking at the graph/standard deviations anomalous results can be identified. These are….”

71. 4) Explain why IN DETAIL, you may have some odd results / what problems you had with the experiment.
Include MINIMUM THREE and it MUST refer back to the method
"One of the reasons that these large standard deviations/anomalous results were obtained could be due to not getting the bung into the test tube quick enough, which meant that some of the gas would have escaped."

72. 5) Explain how you could improve the experiment if you had to do it again IN DETAIL. Suggest AT LEAST THREE things. Include a diagram and explain why.
"The experiment could be repeated using a data logger to measure the pH, because it was hard to tell if the solution was pH 6 or 7".

73. 6) Explain what further experiments you could do in the future, if you had the time.
"If this investigation could be extended, the effect of temperature on the rate of reaction would compliment the data obtained in this experiment.. This could be done by…"